The present invention relates to a strength-saving structure for a foldable treadmill exerciser. The strength-saving structure includes two torque springs respectively disposed at the bottoms of two sides of a support stand. The torque strings are prestressed to fold back a movable frame body equipped with a running belt. Accordingly, the frame body may be upwardly folded by the prestressed torque springs and the resistive force of gravity is substantially offset thereby so that a user can upwardly fold the frame body without undue physical strain.
FIG. 6 shows a known treadmill exerciser including an upright support stand 80 and a horizontal movable frame body 90 disposed at the bottom of the support stand 80. Rollers 91 are mounted on the front and rear parts of the frame body 90 for retaining an endless running belt 92 thereon. A running board 93 is disposed within the running belt 92 to provide slidable support.
The rear end of the frame body 90 can be turned upward to save room when not in use. Generally, a pneumatic cylinder 94 is mounted at each side of a base seat 81 of the support stand 80. One end of the pneumatic cylinder 94 is connected to the bottom of one side of the frame body 90, while the other end of the pneumatic cylinder 94 is connected to the base seat 81. When folding the frame body 90 upward, the pneumatic cylinder 94 provides a pushing force to assist a user, permitting him or her to conserve strength.
The pneumatic cylinder 94 is equipped with an inner rubber or plastic 0-ring seal (not shown) to avoid leakage of air. However, rubber or plastic material, when subjected to temperature, humidity, light and abrasion, naturally tends to age and deform. Therefore, the internal air in the cylinder 94 often escapes after a period of use, causing the pneumatic cylinder to diminish in its functional capability. Although the pneumatic cylinder 94 could be entirely replaced in that event, the price of such pneumatic cylinder typically increases with its required length. The total weight of the frame body 90 and the peripheral components is considerable (often over 15 kgxcx9c20 kg) such that were the air of the pneumatic cylinder 94 to leak, the resultant fall of the frame body 90 could seriously injure the user. To prevent this, a longer pneumatic cylinder is preferred. Hence, replacing such pneumatic cylinder becomes very expensive. In addition, it is impossible to replace simply the O-ring inside the pneumatic cylinder; and full replacement of a faulty pneumatic cylinder is invariably necessary.
It is therefore a primary object of the present invention to provide a strength-saving structure for folding a treadmill exerciser in which two prestressed torque springs are respectively fitted around circular tubes of support bars to impart an upward folding force for the movable frame body. Therefore, when the frame body is in its folded stowed position, the prestressed torque springs serve to retain the frame body in that position against the force of gravity, so that the danger of sudden unfolding caused by the gravity is reduced. Also, after use, a user is assisted by the torque springs to easily upward fold the frame body, lifting its rear part without much physical exertion.
It is a further object of the present invention to provide the above strength-saving structure for folding a treadmill exerciser to a stowed configuration in which a circular tube and an arch board of a support bar define an arch rail in which a projecting board of the frame body is slidably fitted. Thus, during folding of the frame body, the generated frictional force is distributed so that the useful life of the folding section is prolonged.
It is still a further object of the present invention to provide the above strength-saving structure for folding a treadmill exerciser in which the torque springs are resistant to damage and are of low cost so that the overall cost for the treadmill exerciser is minimized.
According to the above objects, the strength-saving structure for a foldable treadmill exerciser of the present invention includes a support stand having a rectangular base seat at its bottom, wherein each lateral side of the base seat is formed with an upwardly extending support bar, a top end of which is connected with each side of a rail.
The inner sides of the support bars are each disposed near their bottom ends with a circular tube protruding therefrom. An arch board open to below is disposed within the circular tube, such that the circular tube and the arch board define therebetween an arch rail. An inwardly projecting engaging pin is disposed at the inner side of each support bar under the circular tube.
A movable frame body is disposed between the two support bars of the support stand. The frame body is substantially rectangular in configuration, having two longitudinally extending long bars and two transversely extending short bars. At the outer sides of the long bars are formed two arch projecting boards open to below, each of which extends into an arch rail defined by a circular tube and its arch board. Two rollers are pivotally disposed between inner sides of bars at front and rear portions of the frame body, and a running belt is retained about them. A running board is disposd within the running belt.
Two torque springs are respectively fitted on the circular tubes of the support bars. The two torque springs are situated to be coiled in different directions, one end of each torque spring having a hook section disposed proximate the bottom of the support bar for hooking the engaging pin beneath the circular tube, and the other end of the torque spring having a backing section extending transversely from its coiled portions. The backing section serves to engage the bottom of the long bar of the frame body.